Previously, sliding doors on aircraft hangars have been equipped with electric-motor operated drives mounted on the inside or outside of the door and having a rubber-tired motor-driven wheel engaging the floor. One problem with such drives is that they project beyond the door at the side of the door (i.e., inside or outside) on which they are mounted. This imposes engineering design limitations on doors of this type in which one "master" leaf (a sliding door section carrying the motorized drive unit) operated several other "slave" leaves (sliding door sections with pickup brackets which cause each successive sliding door section to engage the next one as they slide open or closed). Usually the master leaf carrying the motor drive is slidable on the outside of the other leaves of the door.